The present invention relates to the use of organic light emitting diode devices for area illumination.
Solid-state lighting devices made of light emitting diodes are increasingly useful for applications requiring robustness and long-life. For example, solid-state LEDs are found today in automotive applications. These devices are typically formed by combining multiple, small LED devices providing a point light source into a single module together with glass lenses suitably designed to control the light as is desired for a particular application (see, for example WO99/57945, published Nov. 11, 1999). These multiple devices are expensive and complex to manufacture and integrate into single area illumination devices. Moreover, LED devices provide point sources of light, a plurality of which are employed for area illumination.
Organic light emitting diodes (OLEDs) are manufactured by depositing organic semiconductor materials between electrodes on a substrate. This process enables the creation of light sources having extended surface area on a single substrate. The prior art describes the use of electro-luminescent materials as adjuncts to conventional lighting (for example U.S. Pat. No. 6,168,282 issued Jan. 2, 2001 to Chien). In this case, because of the limited light output from the electro-luminescent material, it is not useful for primary lighting.
EP1120838A2, published Aug. 1, 2001, describes a method for mounting multiple organic light emitting devices on a mounting substrate to create a light source. However, this approach of mounting multiple light sources on a substrate increases the complexity and hence the manufacturing costs of the area illumination light source. Moreover, in this design the multiple substrates are not readily replaced by consumers if they should fail. In addition, each lighting device must be readily and safely replaced by consumers at minimal cost.
There is a need therefore for an improved, replaceable OLED area illumination device having a simple construction using a single substrate and compatibility with the existing lighting infrastructure.
The need is met according to the present invention by providing a solid-state area illumination lighting apparatus that includes a plurality of light sources, each light source having, a substrate; an organic light emitting diode (OLED) layer deposited upon the substrate, the organic light emitting diode layer including first and second electrodes for providing electrical power to the OLED layer; an encapsulating cover covering the OLED layer; and first and second conductors located on the substrate and electrically connected to the first and second electrodes, and extending beyond the encapsulating cover for making electrical contact to the first and second electrodes by an external power source; and a lighting fixture for removably receiving and holding the plurality of light sources and having a plurality of first electrical contacts for making electrical connection to the first and second conductors of the light sources, and second electrical contacts for making electrical connection to an external power source.
The present invention has the advantage of providing a fixture together with inexpensive, long-lived, highly efficient light sources that are replaceable, and are compatible with the existing lighting infrastructure and requirements.